Imaging lens and imaging device provided with the same

ABSTRACT

An imaging lens substantially consists of five lenses consisting of, in order from the object side: a first lens having a positive refractive power and having a meniscus shape with the convex surface toward the object side; a second lens having a biconcave shape; a third lens having a positive refractive power and having a meniscus shape with the convex surface toward the image side; a fourth lens having a positive refractive power and having a convex surface toward the image side; and a fifth lens having a negative refractive power, wherein a predetermined conditional expression is satisfied.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to JapanesePatent Application No. 2013-195414, filed on Sep. 20, 2013. The aboveapplication is hereby expressly incorporated by reference, in itsentirety, into the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fixed-focus imaging lens that formsan optical image of a subject on an image sensor, such as a CCD (ChargeCoupled Device) or CMOS (Complementary Metal Oxide Semiconductor), andan imaging device that is provided with the imaging lens and performsimaging, such as an imaging device incorporated in a digital stillcamera, a mobile phone with camera, a PDA (Personal Digital Assistance),a smartphone, a tablet-type terminal, a portable video game player, etc.

2. Description of the Related Art

Along with the spread of personal computers in ordinary homes, etc.,digital still cameras that are capable of inputting image information,such as photographed landscapes and portraits, to a personal computerare also rapidly spreading. Further, more and more mobile phones,smartphones and tablet-type terminals are equipped with a camera modulefor inputting images. The above-mentioned devices capable of imaging usean image sensor, such as a CCD or CMOS. In recent years, such imagesensors are becoming more compact, and there are also demands forcompact imaging devices and compact imaging lenses to be incorporated inthe imaging devices. At the same time, pixel density of such imagesensors is also becoming higher, and imaging lenses with higherresolution and higher performance are demanded. For example, performancethat can accommodate a high pixel density of 5 megapixel or more, ormore preferably 8 megapixel or more is demanded.

In order to meet the above-described demands, an imaging lens formed bya relatively large number of lenses, namely, having a five-lensconfiguration may be provided. For example, each of U.S. Pat. No.8,395,851 and U.S. Patent Application Publication No. 20130201567(hereinafter, Patent Documents 1 and 2, respectively) proposes animaging lens with a five-lens configuration including, in order from theobject side, a first lens having a positive refractive power, a secondlens having a negative refractive power, a third lens having a positiverefractive power, a fourth lens having a positive refractive power, anda fifth lens having a negative refractive power.

SUMMARY OF THE INVENTION

On the other hand, for an imaging lens for use, in particular, withdevices that are becoming thinner and thinner, such as PDAs, smartphonesand tablet-type terminals, it is desired to accomplish an imaging lenswith a large image size that is sufficient for accommodating alarge-size image sensor that meets the demand for higher resolution,while achieving reduction of the entire length of the lens. The entirelength of the imaging lens disclosed in each of Patent Documents 1 and 2is long relative to the image size, and it is difficult to achievereduction of the entire length of the lens when these lenses are appliedto an image sensor that satisfies the demand for higher resolution.

In view of the above-described circumstances, the present invention isdirected to providing an imaging lens having a large image sizesufficient for accommodating an image sensor having a size that meetsthe demand for higher resolution, and capable of achieving high imagingperformance throughout from the central angle of view to the peripheralangle of view, while achieving reduction of the entire length of thelens, and an imaging device provided with the imaging lens and capableof capturing high-resolution images.

An imaging lens according to a first aspect of the inventionsubstantially consists of five lenses consisting of, in order from theobject side: a first lens having a positive refractive power and havinga meniscus shape with the convex surface toward the object side; asecond lens having a biconcave shape; a third lens having a positiverefractive power and having a meniscus shape with the convex surfacetoward the image side; a fourth lens having a positive refractive powerand having a convex surface toward the image side; and a fifth lenshaving a negative refractive power, wherein the conditional expressionbelow is satisfied:

0.4<f/f4<2  (1),

where f is a focal length of the entire system, and f4 is a focal lengthof the fourth lens.

An imaging lens according to second aspect of the inventionsubstantially consists of five lenses consisting of, in order from theobject side: a first lens having a positive refractive power and havinga meniscus shape with the convex surface toward the object side; asecond lens having a biconcave shape; a third lens having a positiverefractive power and having a meniscus shape with the convex surfacetoward the image side; a fourth lens having a positive refractive powerand having a convex surface toward the image side; and a fifth lenshaving a negative refractive power, wherein the conditional expressionbelow is satisfied:

−8<f·tan ω/L4r<−0.4  (2),

where f is a focal length of the entire system, ω is a half angle ofview, and L4r is a paraxial radius of curvature of an image-side surfaceof the fourth lens.

It should be noted that, with respect to the imaging lens of the firstand the second aspects of the invention, the expression “substantiallyconsisting of five lenses” means that the imaging lens of the inventionmay include, in addition to the five lenses: lenses substantiallywithout any power; optical elements other than lenses, such as a stopand a cover glass; mechanical components, such as a lens flange, a lensbarrel, an image sensor, and a camera shake correcting mechanism; etc.It should be noted that the sign (positive or negative) with respect tothe surface shape or the refractive power of any lens having an asphericsurface of the above-described lenses is about the paraxial region.

When the imaging lens of the first and the second aspects of theinvention further employs and satisfies the following preferredfeatures, even higher optical performance can be achieved.

In the imaging lens of the first and the second aspects of theinvention, it is preferred that the fifth lens have a concave surfacetoward the image side.

In the imaging lens of the first and the second aspects of theinvention, it is preferred that an image-side surface of the fifth lenshave at least one inflection point.

It is preferred that the imaging lens of the first aspect of theinvention satisfy any of the conditional expressions (1-1) to (8) below:

0.4<f/f4<2  (1),

0.5<f/f4<1.7  (1-1),

−8<f·tan ω/L4r<−0.4  (2),

−6<f·tan ω/L4r<−1.4  (2-1),

−3<f/f5<−0.72  (3),

−2.5<f/f5<−1  (3-1),

−2<f/f5<−1.1  (3-2),

0.05<(L4f−L4r)/(L4f+L4r)<2  (4),

0.12<(L4f−L4r)/(L4f+L4r)<1  (4-1),

−3<f/f2<−0.55  (5),

−2.5<f/f2<−0.65  (5-1),

−2<f/f23<−0.4  (6),

−1.5<f/f23<−0.55  (6-1),

0.4<f·tan ω/L5r<10  (7),

0.5<f·tan ω/L5r<5  (7-1), and

1.2<TTL/(f·tan ω)<1.65  (8),

where ω is a half angle of view, f is a focal length of the entiresystem, f2 is a focal length of the second lens, f4 is a focal length ofthe fourth lens, f5 is a focal length of the fifth lens, f23 is acombined focal length of the second lens and the third lens, L4f is aparaxial radius of curvature of the object-side surface of the fourthlens, L4r is a paraxial radius of curvature of the image-side surface ofthe fourth lens, L5r is a paraxial radius of curvature of the image-sidesurface of the fifth lens, and TTL is a distance from the object-sidesurface of the first lens to the image plane, where the back focusportion of the distance is an equivalent air distance. In preferredaspects of the first aspect of the invention, any one or any combinationof the conditional expressions (1-1) to (8) may be satisfied. It ispreferred that the imaging lens of the second aspect of the inventionsatisfy any of the conditional expressions (1), (1-1) and (2-1) to (8).In preferred aspects of the second aspect of the invention, any one orany combination of conditional expressions (1), (1-1) and (2-1) to (8)may be satisfied.

The imaging device according to the invention comprises the imaging lensof the first or the second aspect of the invention.

According to the imaging lens of the first and the second aspects of theinvention, which has the five lens configuration as a whole, theconfiguration of each lens element, in particular, the shape of each ofthe first to the fifth lenses is optimized, thereby accomplishing a lenssystem having a large image size applicable to an image sensor thatsatisfies the demand for higher resolution and having high imagingperformance throughout from the central angle of view to the peripheralangle of view, while achieving reduction of the entire length of thelens.

Further, the imaging device of the invention outputs an imaging signalaccording to an optical image formed by the imaging lens with highimaging performance of the first or the second aspects of the invention,and therefore can capture high-resolution images.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lens sectional view illustrating a first configurationexample of an imaging lens according to one embodiment of the inventionand corresponding to Example 1,

FIG. 2 is a lens sectional view illustrating a second configurationexample of the imaging lens according to one embodiment of the inventionand corresponding to Example 2,

FIG. 3 is a lens sectional view illustrating a third configurationexample of the imaging lens according to one embodiment of the inventionand corresponding to Example 3,

FIG. 4 is a lens sectional view illustrating a fourth configurationexample of the imaging lens according to one embodiment of the inventionand corresponding to Example 4,

FIG. 5 is a lens sectional view illustrating a fifth configurationexample of the imaging lens according to one embodiment of the inventionand corresponding to Example 5,

FIG. 6 is a lens sectional view illustrating a sixth configurationexample of the imaging lens according to one embodiment of the inventionand corresponding to Example 6,

FIG. 7 is a lens sectional view illustrating optical paths through theimaging lens shown in FIG. 1,

FIG. 8 is an aberration diagram showing various aberrations of theimaging lens according to Example 1 of the invention, where sphericalaberration is shown at “A”, astigmatism (field curvature) is shown at“B”, distortion is shown at “C”, and lateral chromatic aberration isshown at “D”,

FIG. 9 is an aberration diagram showing various aberrations of theimaging lens according to Example 2 of the invention, where sphericalaberration is shown at “A”, astigmatism (field curvature) is shown at“B”, distortion is shown at “C”, and lateral chromatic aberration isshown at “D”,

FIG. 10 is an aberration diagram showing various aberrations of theimaging lens according to Example 3 of the invention, where sphericalaberration is shown at “A”, astigmatism (field curvature) is shown at“B”, distortion is shown at “C”, and lateral chromatic aberration isshown at “D”,

FIG. 11 is an aberration diagram showing various aberrations of theimaging lens according to Example 4 of the invention, where sphericalaberration is shown at “A”, astigmatism (field curvature) is shown at“B”, distortion is shown at “C”, and lateral chromatic aberration isshown at “D”,

FIG. 12 is an aberration diagram showing various aberrations of theimaging lens according to Example 5 of the invention, where sphericalaberration is shown at “A”, astigmatism (field curvature) is shown at“B”, distortion is shown at “C”, and lateral chromatic aberration isshown at “D”,

FIG. 13 is an aberration diagram showing various aberrations of theimaging lens according to Example 6 of the invention, where sphericalaberration is shown at “A”, astigmatism (field curvature) is shown at“B”, distortion is shown at “C”, and lateral chromatic aberration isshown at “D”,

FIG. 14 shows an imaging device in the form of a mobile phone terminalprovided with the imaging lens according to the invention, and

FIG. 15 shows an imaging device in the form of a smartphone providedwith the imaging lens according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the drawings.

FIG. 1 shows a first configuration example of an imaging lens Laccording to a first embodiment of the invention. This configurationexample corresponds to a lens configuration of a first numerical example(shown in Tables 1 and 2), which will be described later. Similarly,FIGS. 2 to 6 show cross-sectional configurations of second to sixthconfiguration examples corresponding to imaging lenses L according tosecond to sixth embodiments, which will be described later. The secondto sixth configuration examples correspond to lens configurations ofsecond to sixth numerical examples (shown in Tables 3 to 12), which willbe described later. In FIGS. 1 to 6, each symbol “Ri” denotes a radiusof curvature of the i-th surface, where the most object-side surface ofthe lens elements is the first surface and the surface number issequentially increased toward the image side (the formed image side),and each symbol “Di” denotes a surface distance between the i-th surfaceand the i+1-th surface along the optical axis Z1. It should be notedthat these configuration examples have the same basic configuration.Therefore the following description is made based on the configurationexample of the imaging lens shown in FIG. 1, and the configurationexamples shown in FIGS. 2 to 6 are described as necessary. FIG. 7 is alens sectional view showing optical paths through the imaging lens Lshown in FIG. 1. FIG. 7 shows optical paths of an axial bundle of rays 2and a bundle of rays 3 at the maximum angle of view from an object pointat infinity.

The imaging lens L according to each embodiment of the invention ispreferably usable with various imaging devices using an image sensor,such as a CCD or CMOS, in particular, relatively small portable terminaldevices, such as digital still cameras, mobile phones with camera,smartphones, tablet-type terminals and PDAs. The imaging lens Lincludes, in order from the object side along the optical axis Z1, afirst lens L1, a second lens L2, a third lens L3, a fourth lens L4, anda fifth lens L5.

FIG. 14 shows the appearance of a mobile phone terminal which is animaging device 1 according to one embodiment of the invention. Theimaging device 1 of the embodiment of the invention includes the imaginglens L of any of the embodiments of the invention, and an image sensor100 (see FIG. 1), such as a CCD, for outputting an imaging signalaccording to an optical image formed by the imaging lens L. The imagesensor 100 is placed in the image plane (image plane R14) of the imaginglens L.

FIG. 15 shows the appearance of a smartphone which is an imaging device501 according to one embodiment of the invention. The imaging device 501of the embodiment of the invention includes a camera unit 541 whichincludes the imaging lens L of any of the embodiments of the inventionand an image sensor 100 (see FIG. 1), such as a CCD, for outputting animaging signal according to an optical image formed by the imaging lensL. The image sensor 100 is placed in the image plane (image plane R14)of the imaging lens L.

Various optical members CG may be provided between the fifth lens L5 andthe image sensor 100 depending on the configuration of the cameraprovided with the lens. For example, a cover glass for protecting theimaging area, and a flat plate-like optical member, such as an infraredcut-off filter, may be provided between the fifth lens L5 and the imagesensor 100. In this case, for example, a flat plate-like cover glasswith a coating having a filter effect, such as an effect of an infraredcut-off filter or ND filter, or a material having the same effect may beused as the optical member CG.

Alternatively, without using any optical member CG, the fifth lens L5may be provided with a coating having the same effect as the opticalmember CG, for example. This allows reduction of the number of partsforming the lens and the entire length of the lens.

It is preferred that the imaging lens L include an aperture stop Stdisposed on the object side of the object-side surface of the secondlens L2. Disposing the aperture stop St on the object side of theobject-side surface of the second lens L2 in this manner allowsminimizing increase of the incidence angle of rays traveling through theoptical system on the image plane (the image sensor), in particular, atthe marginal area of the imaging area. In order to enhance this effect,it is preferred that the aperture stop St be disposed on the object sideof the object-side surface of the first lens L1. It should be noted thatthe description “disposed on the object side of the object-side surfaceof the second lens” means that the position of the aperture stop alongthe optical axis direction is the same position as the intersectionbetween a marginal axial ray and the object-side surface of the secondlens L2 or a position nearer to the object side than the intersection.Similarly, “disposed on the object side of the object-side surface ofthe first lens” means that the position of the aperture stop along theoptical axis direction is the same position as the intersection betweena marginal axial ray and the object-side surface of the first lens L1 ora position nearer to the object side than the intersection.

In the case where the aperture stop St is disposed on the object side ofthe object-side surface of the first lens L1 along the optical axisdirection, it is preferred that the aperture stop St be disposed on theimage side of the apex of the surface of the first lens L1. When theaperture stop St is disposed on the image side of the apex of thesurface of the first lens L1 in this manner, reduction of the entirelength of the imaging lens L including the aperture stop St can beachieved. It should be noted that the imaging lenses L according to thefirst, third and sixth embodiments (FIGS. 1, 3 and 6) are configurationexamples where the aperture stop St is disposed on the object side ofthe object-side surface of the first lens L1, and the aperture stop Stis disposed on the image side of the apex of the surface of the firstlens L1. However, these embodiments are not intended to limit theinvention, and the aperture stop St may be disposed on the object sideof the apex of the surface of the first lens L1. Disposing the aperturestop St on the object side of the apex of the surface of the first lensL1 is somewhat disadvantageous in view of ensuring peripheral brightnessthan disposing the aperture stop St on the image side of the apex of thesurface of the first lens L1. However, this preferably allows furtherminimizing increase of the incidence angle of rays traveling through theoptical system on the image plane (the image sensor) at the marginalarea of the imaging area. It should be noted that the aperture stop Stshown in the drawings does not necessarily represent the size and shapethereof, but represents the position thereof along the optical axis Z1.

Alternatively, the aperture stop St may be disposed between the firstlens L1 and the second lens L2 along the optical axis direction, as withthe imaging lens L according to the second, the fourth and the fifthembodiments (FIGS. 2, 4 and 5). In this case, successful correction offield curvature can be achieved. Disposing the aperture stop St betweenthe first lens L1 and the second lens L2 along the optical axisdirection is disadvantageous in view of ensuring telecentricity (thatis, making the principal ray parallel to the optical axis as much aspossible (making the incidence angle on the imaging area near to zero))than disposing the aperture stop St on the object side of theobject-side surface of the first lens L1 along the optical axisdirection. However, preferable optical performance can be achieved byapplying an image sensor, which has recently been accomplished alongwith the development of the image sensor technique, with reduceddegradation of light reception efficiency and reduced color mixing dueto increase of the incidence angle from those of conventional imagesensors.

In this imaging lens L, the first lens L1 has a positive refractivepower in the vicinity of the optical axis, and has a meniscus shape withthe concave surface toward the image side in the vicinity of the opticalaxis. This allows making the position of the posterior principal pointof the first lens L1 nearer to the object side, thereby preferablyallowing reduction of the entire length of the lens.

The second lens L2 has a negative refractive power in the vicinity ofthe optical axis. This allows successful correction of sphericalaberration and longitudinal chromatic aberration that occur when raystravel through the first lens L1. Further, the second lens L2 has abiconcave shape in the vicinity of the optical axis. The second lens L2having a biconcave shape in the vicinity of the optical axis preferablyallows correction of spherical aberration and axial chromaticaberration.

The third lens L3 has a positive refractive power in the vicinity of theoptical axis. This allows successful correction of spherical aberration.Further, the third lens L3 has a meniscus shape with the convex surfacetoward the image side in the vicinity of the optical axis. The thirdlens L3 having a meniscus shape with the convex surface toward the imageside in the vicinity of the optical axis preferably allows correction ofastigmatism, which tends to occur along with reduction of the entirelength of the lens, and this facilitates reduction of the entire lengthof the lens and achieving wider angle of view.

The fourth lens L4 has a positive refractive power in the vicinity ofthe optical axis. The fourth lens L4 having a positive refractive powerin the vicinity of the optical axis preferably allows reduction of theentire length of the lens. Further, the fourth lens L4 has a convexsurface toward the image side in the vicinity of the optical axis. Thefourth lens L4 having a positive refractive power in the vicinity of theoptical axis and having a convex surface toward the image side in thevicinity of the optical axis preferably allows correction ofastigmatism, which tend to occur along with reduction of the entirelength of the lens, and this facilitates reduction of the entire lengthof the lens and achieving wider angle of view. Further, as shown in eachembodiment, it is preferred that the fourth lens L4 have a meniscusshape with the convex surface toward the image side in the vicinity ofthe optical axis. The fourth lens L4 having a meniscus shape with theconvex surface toward the image side in the vicinity of the optical axisis advantageous for correction of astigmatism.

The fifth lens L5 has a negative refractive power in the vicinity of theoptical axis. Regarding the first to the fourth lenses L1 to L4 as onepositive optical system, the fifth lens L5 having a negative refractivepower makes the imaging lens L as a whole a telephoto configuration.This allows making the position of the posterior principal point of theentire imaging lens L nearer to the object side, thereby preferablyallowing reduction of the entire length of the lens. Also, the fifthlens L5 having a negative refractive power in the vicinity of theoptical axis allows successful correction of field curvature.

Further, as shown in each embodiment, it is preferred that the fifthlens L5 have a concave surface toward the image side in the vicinity ofthe optical axis. The fifth lens having a concave surface toward theimage side in the vicinity of the optical axis is advantageous forreduction of the entire length of the lens. Further, as shown in eachembodiment, it is preferred that the fifth lens L5 have a concavesurface toward the image side in the vicinity of the optical axis, andthe image-side surface of the fifth lens L5 have an aspheric shapehaving at least one inflection point. In this case, increase of theincidence angle of rays traveling through the optical system on theimage plane (the image sensor), in particular, at the marginal area ofthe imaging area can be minimized. It should be noted that the“inflection point” of the image-side surface of the fifth lens L5 refersto a point where the shape of the image-side surface of the fifth lensL5 changes from a convex shape to a concave shape (or from a concaveshape to a convex shape) toward the image side. The position of theinflection point can be any position within an effective radius of theimage-side surface of the fifth lens L5 along the radial direction fromthe optical axis.

Further, as shown in the first and the second embodiments, it ispreferred that the fifth lens L5 have a biconcave shape in the vicinityof the optical axis. In this case, a sufficiently strong negativerefractive power of the fifth lens L5 can be achieved while minimizingincrease of the absolute value of the curvature of each surface of thefifth lens L5. Also, the fifth lens L5 having a biconcave shape in thevicinity of the optical axis allows more successful correction ofdistortion. Further, as shown in the third to the sixth embodiments, itis preferred that the fifth lens L5 have a meniscus shape with theconcave surface toward the image side in the vicinity of the opticalaxis. This facilitates making the position of the posterior principalpoint of the entire system nearer to the object side, thereby preferablyallowing reduction of the entire length of the lens.

According to the above-described imaging lens L, which has the five lensconfiguration as a whole, the configuration of each of the lenselements, the first to the fifth lenses L1 to L5, is optimized, therebyaccomplishing a lens system having a large image size applicable to animage sensor that satisfies the demand for higher resolution and havinghigh imaging performance throughout from the central angle of view tothe peripheral angle of view, while achieving reduction of the entirelength of the lens.

In order to achieve even higher performance, it is preferred that eachof the first to the fifth lenses L1 to L5 of the imaging lens L have anaspheric surface on at least one side thereof.

Further, it is preferred that each of the lenses L1 to L5 forming theimaging lens L be a single lens rather than a cemented lens. In thiscase, the number of aspheric surfaces is greater than that in a casewhere any of the lenses L1 to L5 are cemented together to form acemented lens. This allows higher freedom of design of each lens,thereby preferably allowing reduction of the entire length of the lens.

Still further, in a case where the lens configuration of each of thefirst to the fifth lenses L1 to L5 forming the imaging lens L is set toprovide, for example, a full angle of view of 70° or more, as with theimaging lenses L according to the first to the fifth embodiment, theimaging lens L is preferably applicable to an image sensor having a sizethat meets the demand for higher resolution and incorporated in a mobilephone, or the like, while achieving reduction of the entire length ofthe lens.

Next, operation and effects related to conditional expressions of theimaging lens L having the above-described configuration are described inmore detail. It is preferred that the imaging lens L satisfy any one orany combination of the conditional expressions described below. It ispreferred that one or more conditional expressions to be satisfied areselected as appropriate depending on requirements on the imaging lens L.

It is preferred that a focal length f4 of the fourth lens L4 and a focallength f of the entire system satisfy the conditional expression (1)below:

0.4<f/f4<2  (1).

The conditional expression (1) defines a preferred numerical range ofthe ratio of the focal length f of the entire system to the focal lengthf4 of the fourth lens L4. When the refractive power of the fourth lensL4 is ensured such that the ratio does not become smaller than or equalto the lower limit of the conditional expression (1), the positiverefractive power of the fourth lens L4 does not become excessively weakrelative to the refractive power of the entire system. This allowsminimizing increase of the incidence angle of rays traveling through theoptical system on the image plane (the image sensor), in particular, atan intermediate angle of view, and preferably achieving correction ofdistortion and lateral chromatic aberration. When the refractive powerof the fourth lens L4 is maintained such that the ratio does not becomegreater than or equal to the upper limit of the conditional expression(1), the positive refractive power of the fourth lens L4 does not becomeexcessively strong relative to the refractive power of the entiresystem, and this allows reduction of the entire length of the lens whileachieving successful correction of, in particular, spherical aberrationand astigmatism. In order to enhance this effect, it is more preferredthat the conditional expression (1-1) below be satisfied, or it is evenmore preferred that the conditional expression (1-2) below be satisfied:

0.5<f/f4<1.7  (1-1), or

0.55<f/f4<1.4  (1-2).

Further, it is preferred that the focal length f of the entire system, ahalf angle of view ω, and a paraxial radius of curvature L4r of theimage-side surface of the fourth lens L4 satisfy the conditionalexpression (2) below:

−8<f·tan ω/L4r<−0.4  (2).

The conditional expression (2) defines a preferred numerical range ofthe ratio of the paraxial image height (f·tan ω) to the paraxial radiusof curvature L4r of the image-side surface of the fourth lens L4. Whenthe paraxial image height (f·tan ω) relative to the paraxial radius ofcurvature L4r of the image-side surface of the fourth lens L4 is setsuch that the ratio does not become smaller than or equal to the lowerlimit of the conditional expression (2), successful correction ofdistortion can be achieved. Further, in the case where the image-sidesurface of the fifth lens L5 has an aspheric shape with a large absolutevalue of curvature or the image-side surface of the fifth lens L5 has anaspheric shape having a concave surface toward the image side and havingat least one inflection point, an effect of minimizing increase of theincidence angle of the principal ray on the imaging plane is obtainedmainly at an intermediate angle of view and the peripheral angle ofview. In this case, when the lower limit of the conditional expression(2) is satisfied, the effect of minimizing increase of the incidenceangle of the principal ray on the imaging plane (the image sensor) isobtained, in particular, at a low angle of view. On the other hand, whenthe paraxial image height (f·tan ω) relative to the paraxial radius ofcurvature L4r of the image-side surface of the fourth lens L4 is setsuch that the ratio does not become greater than or equal to the upperlimit of the conditional expression (2), successful correction ofspherical aberration can be achieved. In order to enhance this effect,it is preferred that the conditional expression (2-1) below besatisfied, or it is more preferred that the conditional expression (2-2)below be satisfied:

−6<f·tan ω/L4r<−1.4  (2-1), or

−5<f·tan ω/L4r<−1.8  (2-2).

It is more preferred that a focal length f5 of the fifth lens L5 and thefocal length f of the entire system satisfy the conditional expression(3) below:

−3<f/f5<−0.72  (3).

The conditional expression (3) defines a preferred numerical range ofthe ratio of the focal length f of the entire system to the focal lengthf5 of the fifth lens L5. When the refractive power of the fifth lens L5is maintained such that the ratio does not become smaller than or equalto the lower limit of the conditional expression (3), the negativerefractive power of the fifth lens L5 does not become excessively strongrelative to the refractive power of the entire system, and thispreferably allows correction of distortion. When the refractive power ofthe fifth lens L5 is ensured such that the ratio does not become greaterthan or equal to the upper limit of the conditional expression (3), thenegative refractive power of the fifth lens L5 does not becomeexcessively weak relative to the refractive power of the entire system,and this is advantageous for reduction of the entire length of the lens.In order to enhance this effect, it is more preferred that theconditional expression (3-1) below be satisfied, or it is even morepreferred that the conditional expression (3-2) below be satisfied:

−2.5<f/f5<−1  (3-1), or

−2<f/f5<−1.1  (3-2).

It is preferred that a paraxial radius of curvature L4f of theobject-side surface of the fourth lens L4 and the paraxial radius ofcurvature L4r of the image-side surface of the fourth lens L4 satisfythe conditional expression (4) below:

0.05<(L4f−L4r)/(L4f+L4r)<2  (4).

The conditional expression (4) defines a preferred numerical range ofeach of the paraxial radius of curvature L4f of the object-side surfaceof the fourth lens L4 and the paraxial radius of curvature L4r of theimage-side surface of the fourth lens L4. When the paraxial radius ofcurvature L4f of the object-side surface of the fourth lens L and theparaxial radius of curvature L4r of the image-side surface of the fourthlens L4 are set such that the above ratio does not become smaller thanor equal to the lower limit of the conditional expression (4),successful correction of spherical aberration can be achieved. When theparaxial radius of curvature L4f of the object-side surface of thefourth lens L4 and the paraxial radius of curvature L4r of theimage-side surface of the fourth lens L4 are set such that the aboveratio does not become greater than or equal to the upper limit of theconditional expression (4), successful correction of astigmatism can beachieved. In order to enhance this effect, it is more preferred that theconditional expression (4-1) below be satisfied, or it is even morepreferred that the conditional expression (4-2) below be satisfied:

0.12<(L4f−L4r)/(L4f+L4r)<1  (4-1), or

0.15<(L4f−L4r)/(L4f+L4r)<0.5  (4-2).

It is more preferred that a focal length f2 of the second lens L2 andthe focal length f of the entire system satisfy the conditionalexpression (5) below:

−3<f/f2<−0.55  (5).

The conditional expression (5) defines a preferred numerical range ofthe ratio of the focal length f of the entire system to the focal lengthf2 of the second lens L2. When the refractive power of the second lensL2 is maintained such that the ratio does not become smaller than orequal to the lower limit of the conditional expression (5), the negativerefractive power of the second lens L2 does not become excessivelystrong relative to the refractive power of the entire system, and thispreferably allows reduction of the entire length of the lens. When therefractive power of the second lens L2 is ensured such that the ratiodoes not become greater than or equal to the upper limit of theconditional expression (5), the negative refractive power of the secondlens L2 does not become excessively weak relative to the refractivepower of the entire system, and this allows successful correction ofspherical aberration and longitudinal chromatic aberration. In order toenhance this effect, it is more preferred that the conditionalexpression (5-1) below be satisfied, or it is even more preferred thatthe conditional expression (5-2) below be satisfied:

−2.5<f/f2<−0.65  (5-1), or

−1.5<f/f2<−0.7  (5-2).

It is preferred that a combined focal length f23 of the second lens L2and the third lens L3 and the focal length f of the entire systemsatisfy the conditional expression (6) below:

−2<f/f23<−0.4  (6).

The conditional expression (6) defines a preferred numerical range ofthe ratio of the focal length f of the entire system to the combinedfocal length f23 of the second lens L2 and the third lens L3. When thecombined focal length f23 of the second lens L2 and the third lens L3 isensured such that the ratio does not become smaller than or equal to thelower limit of the conditional expression (6), the combined negativerefractive power of the second lens L2 and the third lens L3 does notbecome excessively strong relative to the refractive power of the entiresystem, and this is advantageous for reduction of the entire length ofthe lens. When the combined focal length f23 of the second lens L2 andthe third lens L3 is maintained such that the ratio does not becomegreater than or equal to the upper limit of the conditional expression(6), the combined negative refractive power of the second lens L2 andthe third lens L3 does not become excessively weak relative to therefractive power of the entire system, and this allows successfulcorrection of spherical aberration and chromatic aberration. In order toenhance this effect, it is more preferred that the conditionalexpression (6-1) below be satisfied, or it is even more preferred thatthe conditional expression (6-2) below be satisfied:

−1.5<f/f23<−0.55  (6-1), or

−1.2<f/f23<−0.6  (6-2).

Further, it is preferred that the focal length f of the entire system,the half angle of view w, and a paraxial radius of curvature L5r of theimage-side surface of the fifth lens L5 satisfy the conditionalexpression (7) below:

0.4<f·tan ω/L5r<10  (7).

The conditional expression (7) defines a preferred numerical range ofthe ratio of the paraxial image height (f·tan ω) to the paraxial radiusof curvature L5r of the image-side surface of the fifth lens. When theparaxial image height (f·tan ω) relative to the paraxial radius ofcurvature L5r of the image-side surface of the fifth lens is set suchthat the ratio does not become smaller than or equal to the lower limitof the conditional expression (7), the absolute value of the paraxialradius of curvature L5r of the image-side surface of the fifth lens L5,which is the most image-side surface of the imaging lens, does notbecome excessively large relative to the paraxial image height (f·tanω), and this allows sufficient correction of field curvature whileachieving reduction of the entire length of the lens. It should be notedthat, in the case where the fifth lens L5 has an aspheric shapeincluding a concave surface toward the image side and at least oneinflection point, as shown by the imaging lens L of each embodiment, andthe lower limit of the conditional expression (7) is satisfied,successful correction of field curvature can be achieved throughout fromthe central angle of view to the peripheral angle of view, and this ispreferable to achieve wider angle of view. When the paraxial imageheight (f·tan ω) relative to the paraxial radius of curvature L5r of theimage-side surface of the fifth lens is set such that the ratio does notbecome greater than or equal to the upper limit of the conditionalexpression (7), the absolute value of the paraxial radius of curvatureL5r of the image-side surface of the fifth lens, which is the mostimage-side surface of the imaging lens, does not become excessivelysmall relative to the paraxial image height (f·tan ω), and this allowsminimizing increase of the incidence angle of rays traveling through theoptical system on the image plane (the image sensor), in particular, atan intermediate angle of view, and also allows minimizing excessivecorrection of field curvature. In order to enhance this effect, it ispreferred that the conditional expression (7-1) below be satisfied:

0.5<f·tan ω/L5r<5  (7-1).

Further, it is preferred that a distance TTL from the object-sidesurface of the first lens L1 to the image plane along the optical axis,where the back focus portion of the distance is an equivalent airdistance, the focal length f of the entire system and the half angle ofview ω satisfy the conditional expression (8) below:

1.2<TTL/(f·tan ω)<1.65  (8).

The conditional expression (8) defines a preferred numerical range ofthe ratio of the distance TTL (the entire length of the lens) from theobject-side surface of the first lens L1 to the image plane along theoptical axis relative to the paraxial image height (f·tan ω). It shouldbe noted that the back focus portion (the distance from the apex of theimage-side surface of the fifth lens L5 to the image plane along theoptical axis) of the entire length of the lens is an equivalent airdistance. When the distance TTL from the object-side surface of thefirst lens L1 to the image plane along the optical axis relative to theparaxial image height (f·tan ω) is maintained such that the ratio doesnot become smaller than or equal to the lower limit of the conditionalexpression (8), excessive correction of field curvature can beminimized. On the other hand, ensuring the distance TTL from theobject-side surface of the first lens L1 to the image plane along theoptical axis relative to the paraxial image height (f·tan ω) such thatthe ratio does not become greater than or equal to the upper limit ofthe conditional expression (8) is advantageous for reduction of theentire length of the lens. In order to enhance this effect, it is morepreferred that the conditional expression (8-1) below be satisfied:

1.3<TTL/(f·tan ω)<1.6  (8-1).

Now, two preferred configuration examples of the imaging lens L andeffects thereof are described. It should be noted that the two preferredconfiguration examples can adopt the above-described preferred featuresof the imaging lens L, as appropriate.

First, the first configuration example of the imaging lens Lsubstantially consists of five lenses consisting of, in order from theobject side: a first lens having a positive refractive power and havinga meniscus shape with the convex surface toward the object side; asecond lens having a biconcave shape; a third lens having a positiverefractive power and having a meniscus shape with the convex surfacetoward the image side; a fourth lens having a positive refractive powerand having a convex surface toward the image side; and a fifth lenshaving a negative refractive power, wherein the conditional expression(1) is satisfied. According to this first configuration example,increase of the incidence angle of rays traveling through the opticalsystem on the image plane (the image sensor) can be minimized, inparticular, at an intermediate angle of view, and successful correctionof distortion, lateral chromatic aberration, spherical aberration andastigmatism can be achieved. This preferably allows achieving an imaginglens having a large image size and having high imaging performancethroughout from the central angle of view to the peripheral angle ofview, while achieving reduction of the entire length of the lens.

The second configuration example of the imaging lens L substantiallyconsists of five lenses consisting of, in order from the object side: afirst lens having a positive refractive power and having a meniscusshape with the convex surface toward the object side; a second lenshaving a biconcave shape; a third lens having a positive refractivepower and having a meniscus shape with the convex surface toward theimage side; a fourth lens having a positive refractive power and havinga convex surface toward the image side; and a fifth lens having anegative refractive power, wherein the conditional expression (2) issatisfied. According to this second configuration example, inparticular, increase of the incidence angle of the principal ray on theimaging plane (image sensor) can be minimized, and this allowssuccessful correction of distortion and spherical aberration. Thispreferably allows achieving an imaging lens having a large image sizeand having high imaging performance throughout from the central angle ofview to the peripheral angle of view, while achieving reduction of theentire length of the lens.

As described above, according to the imaging lens L of the embodimentsof the invention, which has the five lens configuration as a whole, theconfiguration of each lens element is optimized, thereby accomplishing alens system having a large image size and having high imagingperformance throughout from the central angle of view to the peripheralangle of view, while achieving reduction of the entire length of thelens.

The imaging lens according to the embodiments of the invention canachieve even higher imaging performance by satisfying theabove-described preferred conditions, as appropriate. The imaging deviceaccording to the embodiments of the invention outputs an imaging signalaccording to an optical image formed by the high-performance imaginglens of the embodiments of the invention, and therefore can capture ahigh-resolution image throughout from the central angle of view to theperipheral angle of view.

Next, specific numerical examples of the imaging lens according to theembodiments of the invention are described. In the followingdescription, several numerical examples are explained at once.

Tables 1 and 2 presented below show specific lens data corresponding tothe configuration of the imaging lens shown in FIG. 1. Specifically,Table 1 shows basic lens data, and Table 2 shows data about asphericsurfaces. The lens data shown in Table 1 is the lens data of the imaginglens according to Example 1, and each value in the column of surfacenumber “Si” is the surface number of the i-th surface, where the mostobject-side surface of the lens elements is the 1st surface (theaperture stop St is the 1st surface) and the number is sequentiallyincreased toward the image side. Each value in the column of radius ofcurvature “Ri”, which corresponds to each symbol “Ri” shown in FIG. 1,is the value (rnm) of radius of curvature of the i-th surface from theobject side. Each value in the column of surface distance “Di” is thesurface distance (mmn) between the i-th surface Si and the i+1-thsurface Si+1 from the object side along the optical axis Z. Each valuein the column of “Ndj” is the value of refractive index with respect tothe d-line (587.6 nm) of the j-th optical element from the object side.Each value in the column of “νdj” is the value of Abbe number withrespect to the d-line of the j-th optical element from the object side.It should be noted that the lens data also shows values the focal lengthf (nn) and the back focus Bf (mm) of the entire system. It should benoted that the value of the back focus Bf is an equivalent air distance.

Each of the first to the fifth lenses L1 to L5 of the imaging lensaccording to Example 1 has aspheric surfaces on both sides. The value ofradius of curvature of each aspheric surface in the basic lens datashown in Table 1 is a value of radius of curvature in the vicinity ofthe optical axis (paraxial radius of curvature).

Table 2 shows aspheric surface data of the imaging lens of Example 1. Ineach value shown as the aspheric surface data, the symbol “E” means thatthe numerical value following the symbol “E” is an exponent with thebase being 10, and that the numerical value before the symbol “E” ismultiplied by the numerical value represented by the exponentialfunction with the base being 10. For example, “1.0E-02” means“1.0×10⁻²”.

As the aspheric surface data, values of coefficients Ai and KA in theformula of aspheric shape expressed as the formula (A) below are shown.More specifically, Z represents a length (mm) of a perpendicular linefrom a point on the aspheric surface at a height h from the optical axisto a plane (a plane perpendicular to the optical axis) tangential to theapex of the aspheric surface.

$\begin{matrix}{Z = {\frac{C \times h^{2}}{1 + \sqrt{1 - {{KA} \times C^{2} \times h^{2}}}} + {\sum\limits_{i}{{Ai} \times h^{i}}}}} & (A)\end{matrix}$

where Z is a depth (mm) of the aspheric surface, h is a distance (mm)from the optical axis to the lens surface (height), C is a paraxialcurvature=1/R (where R is a paraxial radius of curvature), Ai is an i-thorder (where i is an integer of 3 or more) aspheric coefficient, and KAis an aspheric coefficient.

Similarly to the lens data of the imaging lens of Example 1, specificlens data corresponding to the configurations of imaging lenses shown inFIGS. 2 to 6 are shown as Examples 2 to 6 in Tables 3 to 12. In theimaging lenses according to Example 1 to 6, each of the first to thefifth lenses L1 to L5 has aspheric surfaces on both sides.

FIG. 8 shows, at “A” to “D”, aberration diagrams of sphericalaberration, astigmatism, distortion, and lateral chromatic aberration(chromatic aberration of magnification), respectively, of the imaginglens of Example 1. Each aberration shown in the aberration diagrams ofspherical aberration, astigmatism (field curvature), and distortion iswith respect to the d-line (the wavelength of 587.6 nm) used as thereference wavelength. The aberration diagrams of spherical aberrationand lateral chromatic aberration also show the aberrations with respectto the F-line (the wavelength of 486.1 nm) and the C-line (thewavelength of 656.3 nm). The aberration diagram of spherical aberrationalso shows the aberration with respect to the g-line (the wavelength of435.8 nm). In the aberration diagram of astigmatism, the aberration inthe sagittal direction (S) is shown in the solid line and the aberrationin the tangential direction (T) is shown in the dotted line. The symbol“Fno.” means “F-number” and the symbol “e” means “half angle of view”.It should be noted that values that vary depending on the wavelength,such as the focal length, are values with respect to the d-line, unlessotherwise noted.

Similarly, the various aberrations of the imaging lenses of Examples 2to 6 are shown at “A” to “D” in FIGS. 8 to 13.

Further, Table 13 shows values relating to the conditional expressions(1) to (8) according to the invention for each of Examples 1 to 6.

As can be seen from the numerical data and the aberration diagrams, animaging lens having large image size and high imaging performance isaccomplished in each example while achieving reduction of the entirelength of the lens.

It should be noted that the numerical values shown in theabove-described tables are rounded at predetermined decimal places. Theunit of the values of angle is degrees and the unit of the values oflength is millimeters; however, this is only one example, and any othersuitable units may be used since optical systems are usable when theyare proportionally enlarged or reduced.

It should be noted that the imaging lens of the invention is not limitedto the above-described embodiments and examples, and various medicationsmay be made to the invention when the invention is carried out. Forexample, the values of the radius of curvature, the surface distance,the refractive index, the Abbe number, the aspheric coefficients, etc.,of each lens component are not limited to the values shown in thenumerical examples and may take different values.

Further, while the imaging lenses of the above-described examples aredescribed on the assumption that they are used as fixed-focus lenses,the imaging lens of the invention can be configured to allow focusing.For example, automatic focusing can be achieved by moving the entirelens system or moving part of the lenses forming the lens system alongthe optical axis.

TABLE 1 Example 1 f = 4.007, Bf = 0.942 Si Ri Di Ndj νdj 1 (aperture ∞−0.240 stop) *2 1.20078 0.600 1.544 55.9 *3 14.70467 0.065 *4 −11.364800.293 1.632 23.4 *5 3.48146 0.280 *6 −10.00069 0.300 1.632 23.4 *7−6.71454 0.580 *8 −2.21997 0.423 1.544 55.9 *9 −1.20934 0.250 *10 −66.71067 0.497 1.544 55.9 *11  1.44624 0.300 12 ∞ 0.250 1.517 64.2 13 ∞0.477 14 (image ∞ plane) *aspheric surface

TABLE 2 Example 1: Aspheric Surface Data Surface No. KA A4 A6 A8 A10 2−3.0398205E+00  2.8123464E−01 −4.4727010E−02 −2.0373113E−01 7.5759860E−01 3 −1.0238544E+01  3.0173843E−02 −6.0410514E−02 4.8982837E−01 −6.2076792E−01 4  9.9999999E+00  8.8527938E−02−2.1424950E−01  1.3345688E+00 −4.0585947E+00 5  9.9999910E+00 3.9010611E−02  5.6482622E−01 −2.3096596E+00  6.1177885E+00 6 9.9999998E+00 −1.0870110E−01 −5.7704049E−02  2.1333147E−01−9.2389730E−01 7  1.0000009E+01 −3.0962616E−02 −2.2876687E−01 5.7587030E−01 −7.6825828E−01 8  3.0117596E+00  3.9554427E−02−9.3431400E−02 −3.1016047E−01  5.9219638E−01 9 −7.2546848E+00−2.0224009E−01  2.5122519E−01 −4.9835510E−01  4.5557641E−01 10−1.9999997E+01 −1.0040430E−01 −3.7213676E−03  2.7156971E−02−9.9388075E−03 11 −1.2363927E+01 −7.4387761E−02  2.7857575E−02−8.8533400E−03  1.2848647E−03 A12 A14 2 −9.7994474E−01  5.8829212E−01 3−6.6940177E−01  1.9123917E+00 4  5.7809720E+00 −2.7985604E+00 5−8.8570822E+00  5.9275059E+00 6  1.6733475E+00 −1.4260978E+00 7 5.0293816E−01 −1.2175845E−01 8 −3.8753059E−01  9.8871445E−02 9−1.7661549E−01  2.4680257E−02 10  1.4893791E−03 −8.4045492E−05 11−5.5218459E−05 −1.5012385E−06

TABLE 3 Example 2 f = 4.007, Bf = 0.909 Si Ri Di Ndj νdj *1 1.213340.648 1.544 55.9 *2 15.38696 0.027 3 (aperture ∞ 0.044 stop) *4−11.76608 0.250 1.632 23.4 *5 3.71918 0.285 *6 −9.99989 0.300 1.632 23.4*7 −7.42341 0.580 *8 −2.11059 0.421 1.544 55.9 *9 −1.13906 0.250 *10 −6.36895 0.507 1.544 55.9 *11  1.78138 0.312 12 ∞ 0.250 1.517 64.2 13 ∞0.432 14 (image ∞ plane) *aspheric surface

TABLE 4 Example 2: Aspheric Surface Data Surface No. KA A4 A6 A8 A10 1−3.2332814E+00 2.8123464E−01 −1.3546848E−01   1.6455427E−01−1.3236840E−01  2 −2.0000000E+01 3.0173843E−02 2.3058518E−02−8.4566594E−02 2.1420549E−01 4 −1.9999990E+01 8.8527938E−021.2603194E−02 −1.3386560E−01 2.0306461E−01 5  1.0000000E+013.9010611E−02 5.3702546E−01 −2.4959473E+00 6.9957047E+00 6 1.0000000E+01 −1.0870110E−01  −1.8415387E−01   8.1957410E−02−1.6181153E−01  7  1.0000000E+01 −3.0962616E−02  −2.0625171E−01  3.6653230E−01 −4.7068916E−01  8  2.7225753E+00 3.9554427E−025.7339612E−02 −5.4072320E−01 8.4953845E−01 9 −4.5056280E+00−2.0224009E−01  3.2796965E−01 −5.0482271E−01 4.1469974E−01 10−2.0000000E+01 −1.0040430E−01  2.0221498E−02  1.2364193E−02−6.0221336E−03  11 −1.3924314E+01 −7.4387761E−02  2.1281630E−02−6.7549282E−03 1.3453118E−03 A12 A14 1  1.1375716E−01 −3.4578044E−02  2−3.8991555E−01 2.6462935E−01 4 −1.8824947E−01 1.4414626E−01 5−1.0379952E+01 6.8480418E+00 6  5.2433038E−01 −8.0178170E−01  7 3.7153257E−01 −8.4760207E−02  8 −5.7271158E−01 1.4967673E−01 9−1.5902757E−01 2.2847865E−02 10  9.8302117E−04 −5.7068337E−05  11−1.7100034E−04 1.1201736E−05

TABLE 5 Example 3 f = 4.041, Bf = 0.996 Si Ri Di Ndj νdj 1 (aperture ∞−0.240 stop) *2 1.22739 0.600 1.544 55.9 *3 16.66942 0.080 *4 −11.112220.250 1.632 23.4 *5 3.37193 0.280 *6 −10.00090 0.315 1.632 23.4 *7−6.64616 0.580 *8 −1.80097 0.423 1.544 55.9 *9 −1.11110 0.327 *10 9.78928 0.479 1.544 55.9 *11  1.32530 0.300 12 ∞ 0.250 1.517 64.2 13 ∞0.531 14 (image ∞ plane) *aspheric surface

TABLE 6 Example 3: Aspheric Surface Data Surface No. KA A4 A6 A8 A10 2−3.3381677E+00 2.8123464E−01 −3.3413343E−02 −2.9948498E−01 8.8512995E−01 3 −2.0000009E+01 3.0173843E−02 −5.7066427E−02 2.5605540E−01 −3.4546171E−01 4 −1.8360256E+01 8.8527938E−02−2.7557653E−01  1.4978768E+00 −4.0549113E+00 5  4.1592871E+003.9010611E−02  6.1201812E−01 −2.5120439E+00  6.4735985E+00 6−2.0000009E+01 −1.0870110E−01  −1.1235219E−01  3.8889601E−01−1.4973461E+00 7  9.8446774E+00 −3.0962616E−02  −1.6409197E−01 4.0907835E−01 −5.7174013E−01 8  1.8692553E+00 3.9554427E−02 8.2430378E−02 −4.9953188E−01  6.9566669E−01 9 −5.0856043E+00−2.0224009E−01   2.7940171E−01 −4.6330350E−01  4.0050573E−01 10 1.0000009E+01 −1.0040430E−01  −5.0118459E−03  2.1849697E−02−7.3116409E−03 11 −8.2715165E+00 −7.4387761E−02   2.7595480E−02−9.6732991E−03  1.8699468E−03 A12 A14 2 −1.0030084E+00 5.1102554E−01 3 8.6542672E−02 4.2674329E−01 4  5.3757986E+00 −2.5727448E+00  5−8.8002747E+00 5.4661814E+00 6  2.6084850E+00 −2.0180162E+00  7 3.8571528E−01 −8.8634714E−02  8 −3.9711980E−01 8.8929039E−02 9−1.5490879E−01 2.2140292E−02 10  1.0176325E−03 −5.3653919E−05  11−1.7511759E−04 6.2835899E−06

TABLE 7 Example 4 f = 3.982, Bf = 0.967 Si Ri Di Ndj νdj *1 1.188190.523 1.544 55.9 *2 13.89063 0.031 3 (aperture ∞ 0.059 stop) *4−12.50141 0.250 1.632 23.4 *5 4.00394 0.325 *6 −2.93085 0.300 1.632 23.4*7 −2.76041 0.580 *8 −1.91282 0.340 1.544 55.9 *9 −1.30162 0.250 *10 13.89063 0.597 1.544 55.9 *11  1.54878 0.300 12 ∞ 0.250 1.517 64.2 13 ∞0.502 14 (image ∞ plane) *aspheric surface

TABLE 8 Example 4: Aspheric Surface Data Surface No. KA A4 A6 A8 A10 1−2.8016071E+00 2.8123464E−01 −1.3583831E−01 3.6639433E−01 −7.6705331E−012 −2.0000000E+01 3.0173843E−02 −7.4814153E−02 2.5316096E−01−4.2885223E−01 4  1.0000009E+01 8.8527938E−02 −1.2755177E−015.6293159E−01 −1.6544743E+00 5  9.9999900E+00 3.9010611E−02 5.2313102E−01 −2.2333088E+00   6.0912109E+00 6  9.7403068E+00−1.0870110E−01  −1.6513291E−01 2.3221987E−01 −6.9392395E−02 7 7.6758054E+00 −3.0962616E−02  −9.9395291E−02 3.1291427E−01−4.2118865E−01 8  1.8303428E+00 3.9554427E−02  3.6054070E−01−7.7818446E−01   6.1259072E−01 9 −6.8475285E+00 −2.0224009E−01  5.5277708E−01 −7.1457420E−01   4.4019942E−01 10 −2.0000000E+01−1.0040430E−01   3.5891893E−03 1.8320707E−02 −6.6792074E−03 11−7.7343857E+00 −7.4387761E−02   1.7812663E−02 −4.9262258E−03  9.9352118E−04 A12 A14 1  1.0000079E+00 −4.9486320E−01  2  2.3677245E−011.4791254E−02 4  2.4393387E+00 −1.2995851E+00  5 −9.2550734E+006.8523991E+00 6 −7.0517155E−01 9.3064790E−01 7  3.9668167E−011.6035839E−03 8 −2.1651654E−01 3.1799260E−02 9 −1.2920250E−011.4585562E−02 10  9.6517485E−04 −5.1929589E−05  11 −1.2447077E−047.2836769E−06

TABLE 9 Example 5 f = 4.036, Bf = 1.031 Si Ri Di Ndj νdj *1 1.243560.656 1.544 55.9 *2 14.67370 0.028 3 (aperture ∞ 0.047 stop) *4−12.19507 0.250 1.632 23.4 *5 3.52045 0.288 *6 −10.00005 0.300 1.63223.4 *7 −6.28014 0.581 *8 −1.77021 0.408 1.544 55.9 *9 −1.12024 0.254*10  12.45856 0.478 1.544 55.9 *11  1.45542 0.400 12 ∞ 0.250 1.517 64.213 ∞ 0.466 14 (image ∞ plane) *aspheric surface

TABLE 10 Example 5: Aspheric Surface Data Surface No. KA A4 A6 A8 A10 1−3.4865254E+00 2.8123464E−01 −1.4685952E−01   1.6008710E−01−7.4076774E−02  2 −1.9999994E+01 3.0173843E−02 2.1803944E−02−6.7382872E−02 1.4158051E−01 4 −2.0000014E+01 8.8527938E−02−2.1365667E−02  −7.0892166E−02 9.9145651E−02 5  1.0000009E+013.9010611E−02 4.8322488E−01  2.1236172E+00 5.4403399E+00 6−1.5274687E+01 −1.0870110E−01  −7.1935173E−02  −−2.0279028E−01 7.8866993E−01 7  8.9594102E+00 −3.0962616E−02  −1.9797321E−01  4.0540867E−01 −5.0341572E−01  8  2.0141031E+00 3.9554427E−021.0601113E−01 −5.7885374E−01 8.3696806E−01 9 −4.4739222E+00−2.0224009E−01  3.3702202E−01 −5.2566254E−01 4.1295067E−01 10 7.5618339E+00 −1.0040430E−01  1.0220725E−02  1.1762887E−02−4.5396113E−03  11 −8.4271895E+00 −7.4387761E−02  1.9593381E−02−4.3748469E−03 3.9931264E−04 A12 A14 1  4.0657025E−03 3.6790663E−02 2−1.9180871E−01 1.0319113E−01 4  3.6043195E−03 −6.8203738E−02  5−7.1723406E+00 4.2258464E+00 6 −1.2040441E+00 5.9278873E−01 7 3.5757933E−01 −7.6585178E−02  8 −5.7335880E−01 1.6334847E−01 9−1.5453380E−01 2.2071384E−02 10  6.6081817E−04 −3.5619483E−05  11 1.0810115E−05 −2.3125074E−06 

TABLE 11 Example 6 f = 3.843, Bf = 1.080 Si Ri Di Ndj νdj 1 (aperture ∞−0.230 stop) *2 1.36426 0.647 1.544 55.9 *3 18.14375 0.080 *4 −28.853190.210 1.650 21.4 *5 3.77563 0.406 *6 −21.51869 0.238 1.650 21.4 *7−11.45090 0.364 *8 −2.05464 0.574 1.544 55.9 *9 −1.03765 0.297 *10 20.06432 0.504 1.530 55.8 *11  1.29036 0.551 12 ∞ 0.200 1.517 64.2 13 ∞0.397 14 (image ∞ plane) *aspheric surface

TABLE 12 Example 6: Aspheric Surface Data Surface No. KA A4 A6 A8 A10 2−3.4006377E+00  2.2172628E−01 −1.2407953E−01   1.3575886E−01−8.3195209E−02 3  1.0000000E+00 −4.5816987E−02 1.2400610E−01−1.4599020E−01  2.0454782E−01 4 −8.9999989E+00 −5.3462678E−022.2277804E−01 −4.5071228E−02 −4.5274167E−01 5 −6.5797776E−01 2.8145658E−02 1.6560053E−01 −3.5004945E−02 −1.4745114E−01 6 4.5210611E+02 −1.5108370E−01 −1.0073188E−01   1.9916719E−01−1.4039032E−01 7  9.3988220E+01 −1.0706321E−01 −6.3557150E−02  9.3853112E−02 −2.0036792E−02 8  1.8534786E+00  7.8723363E−021.5488795E−02 −1.7474253E−01  2.1764941E−01 9 −2.5739608E+00−2.4392438E−02 5.4516840E−02 −7.7444005E−02  4.7737040E−02 10 1.0000000E+00 −2.6646448E−02 −1.9148505E−02   8.3518124E−03−6.6539755E−04 11 −6.9217794E+00 −4.6782156E−02 1.2516841E−02−4.6597727E−03  1.0382126E−03 A12 A14 2  3.9895256E−02 −9.8107378E−03 3−2.7379359E−01  1.7253749E−01 4  6.5193559E−01 −2.7293723E−01 5 2.0998357E−01  4.3756024E−02 6  5.6236977E−02 — 7  1.9382039E−02 — 8−1.1202135E−01  2.2671933E−02 9 −1.2924309E−02  1.0797829E−03 10−1.1204555E−04  1.5702424E−05 11 −1.3650096E−04  8.0180736E−06

TABLE 13 Values Relating to Conditional Expressions No. ConditionalExpression Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 1f/f4 0.942 1.015 0.922 0.636 0.879 1.195 2 f · tanω/L4r −2.461 −2.613−2.672 −2.297 −2.666 −2.821 3 f/f5 −1.544 −1.600 −1.406 −1.222 −1.312−1.463 4 (L4f − L4r)/(L4f + L4r) 0.295 0.299 0.237 0.190 0.225 0.329 5f/f2 −0.957 −0.902 −0.994 −0.835 −0.940 −0.750 6 f/f23 −0.803 −0.789−0.832 −0.704 −0.755 −0.632 7 f · tanω/L5r 2.058 1.671 2.240 1.931 2.0522.269 8 TTL/(f · tanω) 1.422 1.418 1.459 1.412 1.447 1.503

It should be noted that the above-described values of the paraxialradius of curvature, the surface distance, the refractive index, and theAbbe number were obtained by measurement performed by an expert inoptical measurement according to the following methods.

The paraxial radius of curvature is obtained by measuring each lensusing an ultra-high precision three-dimensional measuring device, UA3P(available from Panasonic Factory Solutions Co., Ltd.), and using thefollowing procedure. Tentative values of a paraxial radius of curvatureR_(m) (where m is a natural number) and a conic constant K_(m) are setand inputted to the UA3P, and an n-th order aspheric coefficient An inthe formula of aspheric shape is calculated from the tentative valuesand the measurement data using a fitting function attached to the UA3P.It is assumed that C=1/R_(m) and KA=K_(m)−1 in the above-describedformula (A) of aspheric shape. Based on R_(m), K_(m), An, and theformula of aspheric shape, the depth Z of the aspheric surface in theoptical axis direction depending on the height h from the optical axisis calculated. Then, for each height h from the optical axis, adifference between the calculated depth Z and the measured depth valueZ′ is calculated, and whether or not the difference is within apredetermined range is determined. If it is determined that thedifference is within the predetermined range, the set value of R_(m) isused as the paraxial radius of curvature. On the other hand, if thedifference is out of the predetermined range, R_(m+1) and K_(m+1) areset by changing at least one of the values of R_(m) and K_(m) used tocalculate the difference, and are inputted to the UA3P to perform theabove-described calculations, and then, for each height h from theoptical axis, whether or not a difference between the calculated depth Zand the measured depth value Z′ is within the predetermined range isdetermined. This operation is repeated until the difference between thecalculated depth Z and the measured depth value Z′ for each height hfrom the optical axis falls within the predetermined range. It should benoted that the predetermined range here is within 200 nm. The range ofthe height h is within the range from 0 to ⅕ of the maximum outerdiameter of the lens.

The surface distance is obtained by measurement using a centralthickness and surface spacing measurement device, OptiSurf (availablefrom Trioptics), for length measurement of an assembled lens.

The refractive index is obtained by measurement using a precisionrefractometer, KPR-2000 (available from Shimadzu Corporation), with asubject temperature of 25° C. A refractive index measured with respectto the d-line (the wavelength of 587.6 nm) is a refractive index Nd.Similarly, a refractive index measured with respect to the e-line (thewavelength of 546.1 nm) is a refractive index Ne, a refractive indexmeasured with respect to the F-line (the wavelength of 486.1 nm) is arefractive index NF, a refractive index measured with respect to theC-line (the wavelength of 656.3 nm) is a refractive index NC, and arefractive index measured with respect to the g-line (the wavelength of435.8 nm) is a refractive index Ng. The Abbe number νd with respect tothe d-line is obtained by calculating νd=(Nd−1)/(NF−NC) by substitutingthe values of Nd, NF and NC obtained by the above-described measurementinto the equation.

What is claimed is:
 1. An imaging lens substantially consisting of fivelenses consisting, in order from an object side: a first lens having apositive refractive power and having a meniscus shape with a convexsurface toward the object side; a second lens having a biconcave shape;a third lens having a positive refractive power and having a meniscusshape with a convex surface toward an image side; a fourth lens having apositive refractive power and having a convex surface toward the imageside; and a fifth lens having a negative refractive power, wherein theconditional expression below is satisfied:0.4<f/f4<2  (1), where f is a focal length of the entire system, and f4is a focal length of the fourth lens.
 2. An imaging lens substantiallyconsisting of five lenses consisting, in order from an object side: afirst lens having a positive refractive power and having a meniscusshape with a convex surface toward the object side; a second lens havinga biconcave shape; a third lens having a positive refractive power andhaving a meniscus shape with a convex surface toward an image side; afourth lens having a positive refractive power and having a convexsurface toward the image side; and a fifth lens having a negativerefractive power, wherein the conditional expression below is satisfied:−8<f·tan ω/L4r<−0.4  (2), where f is a focal length of the entiresystem, ω is a half angle of view, and L4r is a paraxial radius ofcurvature of an image-side surface of the fourth lens.
 3. The imaginglens as claimed in claim 2, wherein the conditional expression below isfurther satisfied:0.4<f/f4<2  (1), where f is a focal length of the entire system, and f4is a focal length of the fourth lens.
 4. The imaging lens as claimed inclaim 1, wherein the conditional expression below is further satisfied:−3<f/f5<−0.72  (3), where f5 is a focal length of the fifth lens.
 5. Theimaging lens as claimed in claim 1, wherein the fifth lens has a concavesurface toward the image side.
 6. The imaging lens as claimed in claim1, wherein an image-side surface of the fifth lens has at least oneinflection point.
 7. The imaging lens as claimed in claim 1, wherein theconditional expression below is further satisfied:0.05<(L4f−L4r)/(L4f+L4r)<2  (4), where L4f is a paraxial radius ofcurvature of an object-side surface of the fourth lens, and L4r is aparaxial radius of curvature of an image-side surface of the fourthlens.
 8. The imaging lens as claimed in claim 1, wherein the conditionalexpression below is further satisfied:−3<f/f2<−0.55  (5), where f2 is a focal length of the second lens. 9.The imaging lens as claimed in claim 1, wherein the conditionalexpression below is further satisfied:−2<f/f23<−0.4  (6), where f23 is a combined focal length of the secondlens and the third lens.
 10. The imaging lens as claimed in claim 1,wherein the conditional expression below is further satisfied:0.4<f·tan ω/L5r<10  (7), where ω is a half angle of view, and L5r is aparaxial radius of curvature of an image-side surface of the fifth lens.11. The imaging lens as claimed in claim 1, wherein the conditionalexpression below is further satisfied:1.2<TTL/(f·tan ω)<1.65  (8), where TTL is a distance from an object-sidesurface of the first lens to an image plane, where a back focus portionof the distance is an equivalent air distance, and ω is a half angle ofview.
 12. The imaging lens as claimed in claim 2, wherein theconditional expression below is further satisfied:−6<f·tan ω/L4r<−1.4  (2-1), where ω is a half angle of view, and L4r isa paraxial radius of curvature of the image-side surface of the fourthlens.
 13. The imaging lens as claimed in claim 1, wherein theconditional expression below is further satisfied:0.5<f/f4<1.7  (1-1), where f4 is a focal length of the fourth lens. 14.The imaging lens as claimed in claim 4, wherein the conditionalexpression below is further satisfied:−2.5<f/f5<−1  (3-1), where f5 is a focal length of the fifth lens. 15.The imaging lens as claimed in claim 7, wherein the conditionalexpression below is further satisfied:0.12<(L4f−L4r)/(L4f+L4r)<1  (4-1), where L4f is a paraxial radius ofcurvature of the object-side surface of the fourth lens, and L4r is aparaxial radius of curvature of the image-side surface of the fourthlens.
 16. The imaging lens as claimed in claim 8, wherein theconditional expression below is further satisfied:−2.5<f/f2<−0.65  (5-1), where f2 is a focal length of the second lens.17. The imaging lens as claimed in claim 9, wherein the conditionalexpression below is further satisfied:−1.5<f/f23<−0.55  (6-1), where f23 is a combined focal length of thesecond lens and the third lens.
 18. The imaging lens as claimed in claim10, wherein the conditional expression below is further satisfied:0.5<f·tan ω/L5r<5  (7-1), where ω is a half angle of view, and L5r is aparaxial radius of curvature of the image-side surface of the fifthlens.
 19. The imaging lens as claimed in claim 14, wherein theconditional expression below is further satisfied:−2<f/f5<−1.1  (3-2), where f5 is a focal length of the fifth lens. 20.An imaging device comprising the imaging lens as claimed in claim 1.